Printing non-Euclidean solids

Geometrically frustrated solids with non-Euclidean reference metric are ubiquitous in biology and are becoming increasingly relevant in technological applications. Often they acquire a targeted con- figuration of incompatibility through surface accretion of mass as in tree growth or dam construction. We use the mechanics of incompatible surface growth to show that geometrical frustration develop- ing during deposition can be fine-tuned to ensure a particular behavior of the system in physiological (or working) conditions. As an illustration, we obtain an explicit 3D printing protocol for arteries, which guarantees stress uniformity under inhomogeneous loading, and for explosive plants, allowing a complete release of residual elastic energy with a single cut. Interestingly, in both cases reaching the physiological target requires the incompatibility to have a topological (global) component.Comment: 5 pages, 4 figure

Least orthogonal distance estimation of simultaneos equations: a simulation experiment

the aim of this work is to estimate the structural parameters of a simultaneous equation system using both the Limited and Full Information Least Orthogonal Distance Estimator (Pieraccini, 1988; Naccarato, 2007). We compare the results - via simulation experiments – of LODE estimates with those obtained by other methods (Maximum Likelihood, Least Squares). LODE estimators appear to be unbiased and (nearly always) more efficient.Simultaneous equations models, Orthogonal distance,

Fine tuning the electro-mechanical response of dielectric elastomers

We propose a protocol to model accurately the electromechanical behavior of dielectric elastomer membranes using experimental data of stress-stretch and voltage-stretch tests. We show how the relationship between electric displacement and electric field can be established in a rational manner from this data. Our approach demonstrates that the ideal dielectric model, prescribing linearity in the purely electric constitutive equation, is quite accurate at low-to-moderate values of the electric field and that, in this range, the dielectric permittivity constant of the material can be deduced from stress-stretch and voltage-stretch data. Beyond the linearity range, more refined couplings are required, possibly including a non-additive decomposition of the electro-elastic energy. We also highlight that the presence of vertical asymptotes in voltage-stretch data, often observed in the experiments just prior to failure, should not be associated with strain stiffening effects, but instead with the rapid development of electrical breakdown

Compression-induced failure of electro-active polymeric thin films

The insurgence of compression induces wrinkling in actuation devices based on EAPs thin films leading to a sudden decrease of performances up to failure. Based on the classical tension field theory for thin elastic membranes, we provide a general framework for the analysis of the insurgence of in-plane compression in membranes of electroactive polymers (EAPs). Our main result is the deduction of a (voltage-dependent) domain in the stretch space which represents tensile configurations. Under the assumption of Mooney-Rivlin materials, we obtain that for growing values of the applied voltage the domain contracts, vanishing at a critical voltage above which the polymer is wrinkled for any stretch configuration. Our approach can be easily implemented in numerical simulations for more complex material behaviors and provides a tool for the analysis of compression instability as a function of the elastic moduli.Comment: (15 pages, 7 figures

Catastrophic thinning of dielectric elastomers

We provide a clear energetic insight into the catastrophic nature of the so-called creasing and pull-in instabilities in soft electro-active elastomers. These phenomena are ubiquitous for thin electro-elastic plates and are a major obstacle to the development of giant actuators; yet they are not completely understood nor modelled accurately. Here, in complete agreement with experiments, we give a simple formula to predict the voltage thresholds for these instability patterns and model their shape, and show that equilibrium is impossible beyond their onset. Our analysis is fully analytical, does not require finite element simulations, and can be extended to include pre-stretch and to encompass any material behaviour

CARATTERIZZAZIONE DEL SILICIO MACROPOROSO COME SUBSTRATO PER COMPONENTI A RADIOFREQUENZA INTEGRATI

Si tenta di risolvere i problemi dell'integrazione di componenti passivi su Silicio studiando un particolare substrato di macropori. Questa struttura risulta essere stabile meccanicamente e puo' essere molto profonda garantendo cosi'una maggiore riduzione delle perdite, inoltre i processi per realizzare il Silicio Macroporoso sono tutti compatibili con le tecnologie standard (CMOS e BiCMOS)

Il futuro nel presente

L’articolo tratta del “Centro di Arti Digitali” (ovvero “Ars Numerica”) di MontBéliard (Francia) e del linguaggio delle arti elettroniche e digitali, - in particolare il ralenti - anche attraverso cenni storici